1. Field of the Invention
The present invention relates generally to gas, oil and gas/oil fired water heaters and boilers of the type having an internal combustion chamber for supplying heat to the closed tank interior of the device.
2. Description of the Prior Art
For many years, typical water heater construction provided for the flow of hot gas through a series of tubes mounted in vertical fashion between top and bottom support plates within the water heater tank. Water was circulated into and out of a chamber in the prior art devices located between the support plates. The water contacted and circulated about the exterior of the vertical tubes to effect heat transfer to heat the water.
The typical prior art gas, oil or gas/oil fired water heater thus featured a non-pressurized, external combustion chamber. The location of the combustion chamber on the exterior of the water heater resulted in lost heat and lower thermal efficiency. Also, the tubes and support plates were not easily accessible, which generally required disassembly of the entire tank for maintenance and replacement.
In U.S. Pat. Nos. 4,465,024; 4,545,329; and 4,938,204; all assigned to the assignee of the present invention, water heater designs are shown which feature one or more submergible, pressurized combustion chambers so that all combustion takes place in the water heater tank interior in a chamber surrounded by water. The resulting designs decrease heat loss and increase the thermal efficiency of the water heaters many times over that which was achievable with the prior art tube and plate arrangement.
The improved water heater designs featured an externally mounted, forced draft burner unit mounted on the exterior of the closed tank at a tank opening so that the burner nozzle extended in the direction of the combustion chamber for heating the combustion chamber. The burner unit had an inlet opening for the intake of air and an integral impeller for creating an overfire pressure within the combustion chamber. The products of combustion were routed from the combustion chamber to the annular chamber of a flue collector which was mounted about the tank opening, and from the annular chamber to the atmosphere. The nozzle of the forced draft burner extended through a flue opening in the flue collector for communication with the interior of the combustion chamber to supply heat to the combustion chamber.
While the above arrangement achieved a desired increase in efficiency, the forced draft burner unit was a heavy, bulky piece of equipment and was somewhat complicated in design. Because of the bulk of the unit, it was typically not possible to ship the burner preassembled with the water heater, requiring field installation. Because the burner nozzle extended through the flue collector opening to communicate with the combustion chamber, it was necessary to provide heavy insulation about the burner nozzle. The bulk of the force draft burner unit contributed to the overall length of the unit.
While prior art "boiler" construction typically featured horizontally arranged tubes instead of vertical tubes, many of the previously mentioned deficiencies existed in such units, particularly those units utilizing forced draft burners.
The present invention has as its object to provide a combination burner and flue gas collector for use in water heaters and boilers having internal combustion chambers of the type previously described.
Another object of the invention is to provide such a combination burner and flue gas collector of smaller overall dimensions than existing forced draft burner units permit, thereby allowing the burner to be assembled with the water heater or boiler at the factory.
Another object of the invention is to provide a combination burner and flue gas collector of simplified design which is more economical to manufacture.
Another object of the invention is to eliminate the heavy insulation which was necessary in the flue collectors of the prior art designs utilizing external, forced draft burners.
Another object of the invention is to provide a combination burner and flue gas collector which is pressurized by a remotely located fan unit connected by a length of conduit to the flue collector.
Another object of the invention is to provide a combination burner and flue gas collector with improved serviceability characteristics.